William George (Willie) Fay (November 12, 1872 - October 27 1947) was an actor and theatre producer who was one of the co-founders of the Abbey Theatre.

Fay was born in Dublin and attended Belvedere College., Dublin. He worked for a time in the 1890s with a touring theatre company in Ireland, Scotland and Wales. When he returned to Dublin, he worked with his brother Frank, staging productions in halls around the city. Finally, they formed W. G. Fay's Irish National Dramatic Company, focused on the development of Irish acting talent.

The brothers participated in the in founding of the Abbey Theatre and were largely responsible for evolving the Abbey style of acting .

After a falling out with the Abbey directors in 1908, the brothers emigrated to the United States to work in theatre there. Willie moved to London in 1914 worked as an actor in on the stage and in films. One of his most notable film roles was as Father Tom in Carol Reed's Belfast-set Odd Man Out (1947), whose cast was dense with actors from the Abbey Theatre. His The Fays of the Abbey Theatre appeared in 1935. He died in London.